The recommended process would look like this: remove the old add-on, restart Blender, install a new version of the add-on and then install the new Core Library. Before installing a new Core Library you need to restart Blender. If you want to update it manually, you need to reinstall it. When there's a new version, you'll be offered an automatic update.
If you have the Internet connection on the machine with Blender, our add-on will check for updates from time to time. You need to open the add-ons preferences pane, find FaceBuilder, click the 'remove' button and relaunch Blender. - How to remove FaceBuilder from Blender?.If you're a macOS user, you'll download a DMG (Apple Disk Image) file, you need to mount it first (double click), the add-on ZIP-file is inside. Please note, that some operating systems and web-browsers unpack downloaded files automatically - to avoid this don’t click the file in the downloads list of your web-browser, just go to Blender and find the add-on file in your downloads folder. In short: you can do this if you open Blender settings, find the 'Add-ons' section, there’s the “Install…” button which you need to press and choose the download add-on ZIP-file. Also, here's the comprehensive written guide. - How to install FaceBuilder add-on into Blender?.
